86 IROC

iTrader: (14)

Car in question is my 2001 SS M6. I have been foolishly been throwing parts at it lately. It has a miss that I can hear and feel. However, it throws no codes - nor does it indicate a missfire when live scanned. Also, if I shut the car off for 5 minutes or less - it will not restart unless I pump the gas pedal about a 1/2 dozen times while cranking. It runs rougher than normal at idle, shakes under a load in gear - so bad that it feels like the car is comming apart. 6th gear is unuseable under 70 MPH. The car ran great up until about 4-5 weeks ago. I've done the obvious stuff, like plugs & wires. Swapped on a different set of known good coil packs to rule that out. It uses no oil, doesn't smoke, or make any funny mechanical noises. Has great oil pressure, runs cool. I am out of ideas...

99TransAm666

iTrader: (6)

Hows your fuel pressure?

jimmyblue

iTrader: (11)

For the first one, they all miss at idle. I put that to closed loop fuel
dithering, gone into the weeds every so often. Fuggedaboudit.

For the second, try relocating your IAT out of the engine bay or at
least set the fans to run at lower temp and after-run to cool the
engine bay.

86 IROC

iTrader: (14)

Perfect. Has a recently installed Racetronix P&P.

ec_nova

iTrader: (5)

definitely sounds fuel related. how many miles are on the car? when was the last time you changed the fuel filter? I would hook up a mechanical gauge and check fuel pressure and start from there

86 IROC

iTrader: (14)

That's fine and dandy, my bitch is that I have been driving the car with no issues until the past 4-5 weeks. It runs like crap, but didn't before the specified time. I have no SES light, no hard codes stored, etc.

ec_nova

iTrader: (5)

I would also put a voltmeter on the TPS and do a full sweep to make sure there isn't a dead spot

86 IROC

iTrader: (14)

88K on the body, FF has maybe 3K miles on it. Around 50K miles on the forged bottom end. Roughly 6K miles on the heads/cam swap. FP checks out fine via a test gauge.

Will check that next. I hadn't thought of that.

Predator T/A

iTrader: (7)

wha tare your long term fuel trims showing on the data log? its sounds like a fuel issue to me also either mechanically or electronically....check to make sure there are no bugs stuck to the MAF or if you have a oiled filter that its not caked with oil.

kwiksilverz28

iTrader: (7)

He also just replaced a bad ECM. I need to hook up to it and look at the iac, tps, the maf and o2's. I did not know about the cranking issue. Interesting. I would like to see fuel pressure / regulator.....

86 IROC

iTrader: (14)

The cranking issue is something new. Mike, I'll catch up with you either Sunday or Tuesday night. Hope it's a cheap/easy fix.

usnfenix

iTrader: (11)

im no expert however i had a similar problem and i replaced my 02 sensors and car started right up afterwards and hasnt had a problem since

badhombre

iTrader: (4)

x2 I just went through an issue with mine idling rougher than normal and having a rough vibration under load, turns out my passenger side o2 came unplugged. much smoother now

86 IROC

iTrader: (14)

Did you have an SES light? Or any stored codes? My 02s maybe have 6K miles on them at most.

kwiksilverz28

iTrader: (7)

Let's hook up and see what they are doing with the new ECM. They won't cause starting issues.....

usnfenix

iTrader: (11)

ive had a constant SES light since my header install, havent had it tuned out yet. but was having all sorts of idle problems untill i figured it out. car just wanted to die i had to give it gas at stoplights to keep it from quiting on me. then day before i figured it out was getting worse misfires and ses light started blinking, which indicates a misfire condition. replaced the o2 and didnt have any issues and idle returned to normal. scanned it a number of times afterwards and only codes i have are for not having cats

Mike Norris

iTrader: (10)

As far as the misfires and no codes, seeing that it has a cam the misfires readings were most likely turned off during tuning and nothing is reported.

If you can get back to whomever tuned it or get help from someone with tuning software and turn the misfire data back on and then you should be able to isolate the cylinder that is missing.

Hope that helps.

Mike Norris

86 IROC

iTrader: (14)

Thank you Mr. Norris, hope Indy is treating you well.

99wssixm6

iTrader: (3)

I was thinking along the same lines at Mr. Norris. Your tune has probably turned off a bunch of mis fire code ses light request and oxygen sensor ses light request. I had the very same thing happen to me right after I reinstalled the passsanger side head. What I found was coolant/water in the oxygen sensor connector. Everything you described as your problems are exactly what I had going on. Might want to check that stuff first.

Have you done a compression test? Could have something going on there. Bent valve, broken spring(cars can still run with a broken valve spring), loose valve seat, etc.

Mr.Nitrous

iTrader: (51)

Do you have a stock tune in the new pcm?